[en] The objective of this study is to investigate effects of precursor concentration on dimensional size, defect state, and gas sensing performance of MoS₂ sheets synthesized by hydrothermal method with various precursor concentrations (0.14-1.4 m) in fixed HCl solution (7 m). The MoS₂ sheets show a defect-rich and strained structure. When precursor concentration is increased, dimensional size of the sheet is increased while the specific surface area of the sheet is decreased. The MoS₂ sensor made with 0.14 m precursor solution exhibits superior sensing performance with high sensitivity (372%) and rapid recovery time (<16 min) at room temperature in a 500 ppm NO₂ gas atmosphere due to enhanced active site resulting from the highest specific surface area. In addition, all MoS₂ samples show a complete recovery after response to NO₂ gas probably related to the defective and strained surface resulting from the use of HCl surfactant. (copyright 2018 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

[en] Falls and fall-related injuries are a significant problem in the elderly population. A number of different approaches for detecting falls and activities of daily living (ADLs) have been conducted in recent years. However, distinguishing between real falls and certain fall-like ADL is often difficult. The aim of this study is to discriminate falls from fall-like ADLs such as jogging, jumping, and jumping down. The distance between two tri-axial accelerometers attached to the abdomen and the sternum was increased from 10 to 30 cm in 10-cm intervals. Experiments for falls and ADLs were performed to investigate the feasibility of the detection system for falls developed in this study. When the distances between the two tri-axial electrometers were 20 and 30 cm, fall-like ADLs were effectively distinguished from falls. The thresholds for three parameters - SVM, Diff Z, and Sum diff Z - were set; falls could be distinguished from ADL action sequences when the SVM value was larger than 4 g (TH1), the Diff Z parameter was larger than 1.25 g (TH2), and the Sum diff Z parameter was larger than 15 m/s (TH3). In particular, when the SVM, Diff Z, and Sum diff Z parameter were sequentially applied to thresholds (TH1, TH2, and TH3), fall-like ADL action sequences were accurately discriminated from falls.

[en] Reactive surface-exposed anatase TiO₂ (a-TiO₂) is highly desirable for applications requiring superior photocatalytic activity. In order to obtain a favorable surface, morphology control of the a-TiO₂ using capping agents has been widely investigated. Herein, we systematically study the effects of different F sources (HF, TiF₄, and NH₄F) as the capping agent on the morphology control and photocatalytic activities of a-TiO₂ in a hydrothermal process. When either HF or TiF₄ was added, large truncated bipyramids formed with the photocatalytically active {001} facet, whereas the NH₄F was not effective for facet control, yielding nanospheres similar to the pure a-TiO₂. The morphology changes were related to the decomposition behaviors of the F sources in the solvent material: HF and TiF₄ decomposed and supplied F⁻ ions before a-TiO₂ nucleation, which changed the nucleation rate and growth direction, leading to the resultant a-TiO₂ morphology. On the other hand, NH₄F supplied F⁻ ions after a-TiO₂ nucleation and could not change the growth behavior. In terms of the photocatalytic effect, the HF- and TiF₄-treated a-TiO₂ effectively decomposed ∼90% and ∼80% of methylene blue, respectively, in 1 h, while ∼60% was decomposed for the NH₄F-treated a-TiO₂. Note that pure a-TiO₂ photocatalytically decomposed only ∼10% of methylene blue over the same time. These results pave the way to precise control of the facet of TiO₂ through using different capping agents. (paper)

[en] Ti-silicate/Si films were synthesized using a solution deposition route, and the effects of a rapid thermal process (RTP) on the microstructure, chemical bonding state, and interfacial layer (IL) properties were investigated and correlated to the permittivity of the films. The precursor solution was prepared from Ti(IV)-isopropoxide and tetraethylorthosilicate, spin-coated on HF-treated Si substrates, dried, pyrolyzed (400 °C), and subjected to the RTP at 700 °C–1000 °C. The Ti-silicate film consisted of Ti-rich and Si-rich silicates after the pyrolysis and phase segregation became significant as the RTP temperature increase. The silicates segregated into TiO₂-like nanocrystals and Si-richer silicate at up to 850 °C, and the TiO₂-like nanocrystals grew remarkably while the Si-richer silicate was converted into nearly pure SiO₂ at 1000 °C. In addition, the Ti content in the Ti-silicate layer decreased due to Ti out-diffusion to the IL and substrate. Based on HRTEM, FT-IR, XPS, and SIMS analyses, we suggest a model of phase segregation with Ti diffusion and demonstrate that the Ti diffusion can be a critical issue in applications of Ti-silicate/Si systems, in addition to other well-known phenomena, including phase segregation, TiO₂ precipitation, or interface properties. - Highlights: • Role of RTP on microstructure and properties of Ti-silicate film was investigated. • Phase segregation and Ti diffusion varied with the RTP. • Effects of the Ti diffusion on the dielectric properties were firstly investigated. • The Ti diffusion seemed to be one of the critical issues in the film applications. • New phase segregation model with Ti diffusion was suggested